Tailoring a CV for one specific job posting should change the summary line, the order and emphasis of a few skills, and which bullet points get pulled forward, not the underlying facts of your work history. The dates, the employers, the education, and what actually happened at each job stay fixed; what moves is which of those true facts gets stated first and in what words, so the posting's own priorities are visible within the first few lines a reader sees.
What changes for a specific posting
The summary line is the section that should change the most, since it is the part of the CV most directly aimed at a specific reader rather than a permanent record of fact. Reordering bullet points within a job entry so the ones closest to the posting's own language come first, without inventing new ones, is the next most useful change. A skills section can shift emphasis too, moving the tools and technologies the posting names toward the top of the list rather than leaving them wherever they happened to land originally.
What stays the same
Job titles, employers, dates, and education stay exactly as they are regardless of which posting the CV is going to. Inventing or exaggerating a responsibility to match a posting's wording crosses from tailoring into misrepresentation, and it is also the kind of change most likely to fall apart in an actual interview, when a follow-up question expects a detail that was never really there. A bullet point can be reordered, re-emphasised, or trimmed for length, but the underlying fact it describes should never change to fit the posting. The overall structure of the CV, which sections appear and in what order, also tends to stay fixed across postings for the same target role; it is the content inside those sections that flexes, not the shape of the document itself.
Illustrative example: before/after summary line for one posting
Generic: "Experienced software engineer with a background in web development and a strong interest in building good products."
Tailored to a posting emphasising backend reliability work: "Backend engineer with experience building and maintaining production services, focused on reliability and clear on-call ownership."
Both sentences describe the same person truthfully. The second one simply states the parts of that truth the posting cares about first, instead of leading with the most general possible description.
A quick process for tailoring without starting over
Read the posting once for its own language, not just its list of requirements, and note two or three phrases it repeats or emphasises. Rewrite the summary line around those two or three ideas, using the posting's own wording where it honestly matches your background. Then scan the bullet points already in the CV for ones that already speak to those same ideas and move them earlier in their section, without adding anything that was not already true before the posting existed. That whole process takes a few minutes once the CV itself is in good shape, and it never requires touching a job entry's dates or employer name. Applying to several postings in the same general direction usually means most of this work only has to happen once, since the same two or three summary ideas tend to serve more than one posting in that direction.
Common overcorrections to avoid
Rewriting the entire CV for one posting, rather than adjusting the few sections that should actually move, usually costs more time than it returns and risks introducing an inconsistency between the new phrasing and the facts underneath it. Copying phrases straight out of a job description without checking they honestly describe your own experience is the other common overcorrection, and the line between reasonable tailoring and keyword stuffing is covered in more detail in matching your CV keywords to a job description. The general rule about what an applicant tracking system actually rewards is covered in writing an ATS-friendly resume, and it points the same direction as the advice here: honest relevance, not volume.
Tailor it now
A few honest, targeted changes usually do more for one specific application than a full rewrite ever would. Open the CV in the editor and start with the summary line, the part most worth changing first.